The present invention relates to a ring installation method and a ring installation jig used for assembling an anti-slip-off ring into a joint part at which a link and a link coupling pin are coupled to each other, when assembling a link chain that constitutes a crawler belt particularly for use in a crawler-mounted construction machine.
As shown in FIG. 9, a known crawler belt 1 for use in construction machines such as hydraulic excavator and bulldozers is comprised of a plurality of track shoes 2 that serve to contact the ground. The track shoes 2 are respectively attached, by means of attachment bolts, to links 4 that constitute an endless link chain 3. This link chain 3 is assembled by successively forcing link-coupling pins 6 (hereinafter simply referred to as xe2x80x9cpinxe2x80x9d) into tubular bushings 5 such that both ends of each pin project outwards from the respective ends of the right and left links 4. In the link chain 3, the adjacent links 4 are articulately connected to each other by the pins 6 at their ends in such a condition that these ends are spaced apart from each other. At the end of each link 4, there are disposed (i) a lubricant sealing member which hermetically seals a lubricant for preventing an internal wear occurring between each pin 6 and each bushing 5 and (ii) a spacer for preventing crushing of the lubricant sealing member so that the lubricant stored within the pin 6 can be supplied to the space between the pin 6 and the bushing 5.
The link chain 3 of such a crawler belt 1 exerts a great force on the pins 6 in a thrusting direction, when the crawler belt 1 is in service. Therefore, each pin 6 is provided with an anti-slip-off means at both ends thereof. A typical anti-slip-off means for the pin 6 is designed such that a groove is inscribed in its circumferential direction in both ends of the pin 6 and an anti-slip-off ring is fitted in each groove so as to prevent the pin 6 from falling out. Herein, an expandable/contractible ring made of an elastic metal material such as snap rings is used as the anti-slip-off ring.
Japanese Patent Application No. 11-182264 (1999) associated with a previous invention filed by the inventors of the present invention discloses a means for preventing slip-off of pins in the link chain of a crawler belt, as a fixing arrangement for crawler belt links and pins. In the previous invention, as shown in FIGS. 10A, 10B, a link chain 3 has annular space sections 9 each of which is formed between the periphery of the open end of a pin insertion hole 7 in each of right and left links 4 and an end of a pin 6. An anti-slip-off ring A is fitted in each annular space section 9 so that the pin 6 is prevented from moving in its axial direction and falling out. For this arrangement, the periphery of the open end of each pin insertion hole 7 has a tapered inner face 7a which gradually expands outwardly from the pin insertion hole 7. The pin 6 has, at both ends thereof, a tapered outer face 6b which faces the tapered inner face 7a. The inclination angle of the tapered outer face 6b with respect to the axial center line of the pin 6 is slightly smaller than the inclination angle of the tapered inner face 7a. Each annular space portion 9 defined by the tapered outer face 6b and the tapered inner face 7a expands outward in a flared fashion. The anti-slip-off ring A is circular in section and assumes the form of a partly cut-away annular ring. In addition, the anti-slip-off ring A is made of an elastic metal material so that it can be expanded and contracted, increasing and decreasing in diameter.
As described earlier, in the conventional crawler belt 1, the anti-slip-off ring A, which is used as a means for preventing the slip-off of the pin 6 for coupling the link chain 3, is formed from an elastic metal material. When mounting the anti-slip-off ring A in a groove formed at an end of the pin or a recess defined by the inclined surfaces, such an operation becomes necessary that the ring A is enlarged (i.e., expanded in diameter) so as to be wider than the diameter of the pin 6 and then pushed inward. In cases where the aforesaid snap ring is fitted in the groove formed at the end of the pin as the anti-slip-off ring, the snap ring is first expanded by widening a ring enlargement hole formed at the ring""s ends, using known pliers which is a specialized tool for mounting a snap ring, and then fitted in the pin engagement groove. In this case, the workman has to manually attach the snap ring one by one. Since the width of the groove into which the ring is to be fitted should be provided with a margin in order to facilitate the fitting of the ring into the groove, the pin moves the distance corresponding to the margin after the installation of the ring. In addition, there is such a risk that if great external force is exerted in a thrusting direction, the anti-slip-off ring or the groove might be broken, resulting in falling out of the pin.
Since the anti-slip-off ring A used in the anti-slip-off means is in the form of a partly cut-out annular ring having a circular section and is made of an elastic metal material, when expanded by a specialized tool similar to the aforesaid priers, the ring A cannot be uniformly enlarged but is just widened at its cut-out portion because of its inherent structure. Therefore, an extremely great power is necessary for the expansion of the ring so that the ring fitting work need to be carried out by substantially two workers and it takes a long time (about 3 minutes) to fit one ring. As a result, sequential operations for coupling a number of links involves prolonged assembling which inevitably entails increased cost. Another problem is that it is currently difficult to automate the process of mounting the anti-slip-off rings.
The present invention is directed to overcoming the above problems and a prime object of the invention is therefore to provide a ring installation method capable of efficiently carrying out an operation when expanding an anti-slip-off ring and mounting it on an end of a link coupling pin, the operation being such that the anti-slip-off ring can be uniformly widened to be fitted on the end of the pin, then pushed until it reaches an engagement position and mounted thereat. Another object of the invention is to provide a ring installation jig used for carrying out the above ring installation method.
In accomplishing the above prime object, there has been provided, in accordance with the invention, a ring installation method for mounting an anti-slip-off ring used for securely attaching a link coupling pin to links in a crawler belt of a vehicle, wherein the anti-slip-off ring is mounted on an annular open space defined between an open end of a pin insertion hole in a link and an insertion end of the pin exposed within the open end, by pressing the anti-slip-off ring against the outer periphery of an end of the pin while the anti-slip-off ring is being expanded and by pushing the anti-slip-off ring in its expanded state with a pusher to slide it from the end of the pin to a predetermined position.
According to the invention, when successively coupling links with coupling pins during a link-chain assembling operation, an anti-slip-off ring is mounted on an insertion end of a pin, the insertion end being exposed within the open end of a pin insertion hole in a link. For installing the anti-slip-off ring, the anti-slip-off ring is firstly expanded from its bore side by use of a ring installation jig so as to be brought into a condition in which the ring can be fitted on the outer periphery of the pin. The ring is then pressed against the outer periphery of the pin""s end. With this procedure, the anti-slip-off ring is substantially uniformly expanded so that it can be easily fitted on the pin. Thereafter, the anti-slip-off ring is slid to a predetermined position on the pin by pushing it with a pusher while the ring is being kept in its expanded condition. This allows the anti-slip-off ring to be pushed to the predetermined position on the end of the pin without difficulty. After the anti-slip-off ring has been pushed into an inwardly tapered-down annular space defined by the open end of the pin insertion hole of the link and the exposed end of the pin, the anti-slip-off ring is contracted so that the ring is readily brought into tight contact with the inner circumferential surface of the pin insertion hole of the link and with the peripheral surface of the pin. As a result, the pin can be fixed so as not to move in a thrusting direction.
According to the invention, for mounting an anti-slip-off ring, which is made of an elastic metal material and partly cut away, on the end of a pin located within a pin insertion hole of a link of a chain, the ring is expanded from its bore side and pressed against the outer periphery of the end of the pin while being kept in the expanded condition and then pushed into a predetermined position, using a pusher. With such two-stage operation, the anti-slip-off ring can be easily, positively installed. Accordingly, the invention has the effect of increasing operational efficiency and therefore workability.
Preferably, the axial center of the anti-slip-off ring is coincident with the axial center of the pin during a process in which the anti-slip-off ring is expanded until its bore becomes larger than the outer diameter of the pin, and kept in the expanded condition. With this arrangement, the two processes, which are the expansion/keeping of the anti-slip-off ring and the pushing/mounting of the anti-slip-off ring, can be continuously carried out by stages on the axial line of the coupling pin so that the anti-slip-off ring can be smoothly installed in the anti-slip-off position without difficulty.
The above-described ring installation method is carried out, in accordance with the invention, by a ring installation jig for mounting an anti-slip-off ring used for securely attaching a link coupling pin to links in a crawler belt of a vehicle,
the jig comprising:
an expansion guide member which has, at its front, a working face to be brought into contact with an end of the pin for positioning and has a ring expansion guide section on its outer periphery and to which a propulsive force is applied;
an expansion claw fitted on the expansion guide member for expanding and supporting the anti-slip-off ring and moving it to the end of the pin;
an elastic body for applying a pressing force to the expansion claw; and
a pusher for pushing the anti-slip-off ring which has been expanded by the expansion claw into an annular open space defined by a link and the pin.
According to the invention, in the process of assembling a link chain which constitutes a crawler belt, the ring installation jig is positioned outside the pin coupling section by a supporting structural member, with its axis being orthogonal to the assembly line of the link chain. After the anti-slip-off ring has been fitted on the outer periphery of the leading end of the expansion claw, the ring installation jig is moved forwards to the end of the pin by a propulsion means, the pin being coupled to the assembled link chain. When the leading end of the expansion guide member has been brought into contact with the end of the pin, the leading end of the expansion guide member fits to a recess formed at the center of the pin""s end with the axial center of the expansion guide member (ring installation jig) being coincident with the axial center of the pin. Then, the ring installation jig is further forwarded by the propulsion means. At that time, while the expansion guide member in contact with the pin""s end is stationary, the expansion claw located outside the expansion guide section is pushed forward by a pressing force imposed on a housed elastic body and, at the same time, radially enlarged by the expansion guide section.
The enlargement of the expansion claw allows the anti-slip-off ring fitted thereon to expand. When the expansion claw stops after advancing until it comes in contact with the pin""s end face, the expansion claw has been enlarged with its bore becoming at least slightly larger than the outer diameter of the pin opposite to the expansion claw. Thereafter, the pusher is urged thereby pushing the anti-slip-off ring which is positioned at the leading end of the pusher, riding on the expansion claw, so that the anti-slip-off ring is shifted onto the pin""s end. As the pusher travels forward by a specified stroke in this condition, the anti-slip-off ring is pushed into the annular space defined by the pin""s end and the opening of the pin insertion hole of the link. In this annular space section, the pin is provided with a groove which is tapered such that the diameter of the pin increases towards its open side. Upon entering this groove, the pushed anti-slip-off ring is released from its expanded condition, decreasing in diameter so that it comes in contact with the inner circumferential surface of the pin insertion hole of the link and with the inclined groove surface of the pin and, consequently, it is securely installed. It should be noted that when the ring installation jig has been moved back after mounting the anti-slip-off ring on the predetermined position of the pin""s end, the pusher as well as the expansion claw are pushed back by the restoring force of the housed elastic body, so that the ring installation jig becomes ready for the next operation.
According to the invention, since the expansion of the anti-slip-off ring and the shift of the anti-slip-off ring onto the pin""s end after the expansion and pushing of it to the predetermined position by the pusher can be carried out serially, the same effect as obtained by the above-described ring installation method can be achieved. Additionally, the ring installation jig of the invention can attain the foregoing object with a simple structure composed of a small number of parts so that it can be manufactured at low cost, contributing a reduction in equipment cost.
The invention is preferably designed such that the ring expansion guide section has sliding surfaces composed of a first tapered circumferential portion, a first circumferential portion, a second tapered circumferential portion and a second circumferential portion respectively, whereas the expansion claw has sliding surfaces composed of a tapered circumferential portion, a first circumferential portion and a second circumferential portion respectively; and such that the tapered circumferential portion, first circumferential portion and second circumferential portion of the expansion claw are in contact with the first tapered circumferential portion, first circumferential portion and second circumferential portion of the ring expansion guide section, respectively. It is preferable that, in the ring expansion guide section, the second tapered circumferential portion and the second circumferential portion have a larger diameter than the first tapered circumferential portion and the first circumferential portion, respectively. This arrangement has such an effect that the expansion of the anti-slip-off ring is carried out by the first tapered circumferential portion, whereas the second tapered circumferential portion and the second circumferential portions positively carry out the shift of the expanded anti-slip-off ring onto the pin""s end by the pusher.
The expansion claw is in the form of a cylinder divided into a plurality of parts and can be moved to the end of the pin with the anti-slip-off ring fitted thereon. With this arrangement, the anti-slip-off ring formed from an elastic metal material can be substantially equally expanded from its bore side and fitting of the anti-slip-off ring on the pin""s end can be more positively carried out. In addition, the elastic body may be made of urethane. Alternatively, the elastic body may be formed from a coil spring. This advantageously makes the entire structure of the ring installation jig small.
Further, it is preferable to dispose the ring installation jig on both sides of an assembly line for the link chain, such that the right and left jigs are positioned with a common axis, facing each other and can be simultaneously actuated. With this arrangement, the anti-slip-off rings can be mounted on both ends of the link coupling pin at the same time, whereby propulsive forces imposed on the pin can be offset to mount the anti-slip-off rings in a stable condition, which consequently enables reasonable operation.